<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<style>
    .box {
        display: flex;
        width: 400px;
        outline: 1px red solid;
    }

    .item-2-1 {
        flex: 1 1;
        padding: 50px;
        background-color: #32d6d6;
        background-clip: content-box;
    }

    .item-2-2 {
        flex: 1 1;
        padding: 20px;
        background-color: #b85ad0;
        background-clip: content-box;
    }
</style>
<body>
<div class="box">
    <div class="item-2-1">1</div>
    <div class="item-2-2">2</div>
</div>
</body>
</html>